Process for crystallizing organic explosive compounds



Patented June 11, 1940 PATENT orrics 3204.059 rnoccss FOR CRYSTALLIZINGoaoamc EXPLOSIVE COMPOUNDS Marshall F. Acken, Woodbury, N. J., assignorto E. I. du Pont de Nemours & Company, Wilmington, DeL, a. corporation01 Delaware No Drawing. Application October 23, 1936, Serial No. 107.147

10 Claims.

The present invention relates to a process for the preparation ofexplosive compounds which normally exist in the form of crystallinesolids. The invention has particular application to the preparation ofpentaerythritol tetranitrate, tetranitraniline, erythritol tetranitrate;mannitol hexanitrate, tetryl and trimethylene trinitramine.

The process of my invention may be adequately illustrated by adiscussion of its application in the preparation of pentaerythritoltetranitrate. The art is familiar with various processes for theformation of the crude pentaerythritol tetranitrate. An early methodcomprised the direct nitration of pentaerythritol in strong nitric acidfollowed by precipitation of the nitrated product with sulfuric acid. Asafer method of nitration was disclosed in U. S. Patent 1,660,651 toMarshall and Bergeim in which process pentaerythritol was dissolved insulfuric acid and the resulting ester was added to nitric acid. Anadditional method of preparation comprised the nitration ofpentaerythritol with mixed sulfuric and nitric acids. 7

The crude pentaerythritol tetranitrate formed by the processes of theprior art was rendered impure and consequently unstable by the presenceof occluded or included matter comprised chiefly of the acids used innitration. A stand- 30 ard method of purification and stabilization wasemployed. After separation from the bulk of the waste acid by drowningin water and filtration, the crude product was washed substantially freefrom acid by means of successive treatments with water and dilute alkalisolution. Further purification was effected by dissolving the washedproduct in acetone, neutralizing any traces of residual acid andprecipitating the purified product from solution by drowning the acetonesolution in 40 a larger amount of water in the presence of means foragitation of the system. The solid product was then recovered byfiltration and dried. The resulting substance was in extremely finelydivided form, being almost clay-like in con- 5 sistency. Whether theagitation during final drowning was slow or fast, the product was stillso fine that 99% passed a 150-mesh screen.

The extreme fineness of the petaerythritol tetranitrate was undesirablein view of the prospective uses for which the material was intended.Pentaerythritol tetranitrate may be employed in fuse manufacture, incommercial blasting exposives, and in explosives adapted to militarypurposes. Specifications for pentaerythritol tetranitrate to be used inthe manufacture of fuse CJI have usually stipulated that the materialmust consist largely of crystals so coarse that they will fail to passthrough the 150-mesh screen. This enhances the free-flowing property ofthe material which was desirable from the standpoint 5 of handling andprocessing. Coarse crystals were also desirable in order that theparticles would not be so fine as to work through and penetrate thecover of the fuse. Apart from the manufacture of fuse, the extremelyfine material was so 10 difficult to handle or charge for any purposethat graining was necessary.

One of the chief objects of my invention is to provide an improvedprocess for the preparation of explosive compounds which normally existin the form of solid crystals. Another object is a process for thepreparation of normally solid crystalline explosive compounds in theform of relatively coarse crystals. An additional object is a processfor the formation of pentaerythritol tetranitrate in relatively coarsecrystals. Other objects will be apparent from the detailed descriptionof my invention which follows.

I have discovered that, upon the gradual addition of cold water, eitherin liquid form or as 5 ice, to a solution of a normally crystallineexplosive compound in an inert organic solvent, relatively coarsecrystals of such compound are formed. For instance, upon the addition ofcold water or ice to a solution of pentaerythritol tetranitrate inacetone, the crystals of pentaerythritol tetranitrate precipitated aremuch larger than those formed in the process of the art in which theacetone solution of the explosive is drowned in a larger body of water.My process 5 comprises a reversal of the drowning process of the art,with the formation of a substantial proportion of crystals which fail topass through a 150-mesh screen. The best results are obtained by thegradual addition of ice to the acetone solution, as illustrated in theexample.

Example The neutralized acetone solution consisting of lbs. ofpentaerythritol tetranitrate in 300 lbs. 5 of acetone was run into anempty drowning tub. The initial temperature of the solution was 90 F.Thirty-five pounds of cracked ice was added and the mixture stirreduntil the ice was completely melted. This procedure was repeated un- 50til lbs. of ice had been added. At this point. the temperature hadfallen to 50 F., and most of the pentaerythritol tetranitrate had beenprecipitated in the form of coarse crystals. Enough water was added tobring the total volume of wa- 56 ter equal to 100 gallons. Thepentaerythritol tetranitrate was then completely precipitated and couldbe handled in the usual way. The following table presents a wet screenanalysis of the product.

Per cent On 48 mesh 8 100 mes 43 150 mes 8 Thru 150 mesh 41 If a coarserproduct is desired the fines may be separated and reworked by the sameprocess. In this way my invention permits the manufacture ofpentaerythritol tetranitrate in crystals coarse enough to meet anyspecification desirable. The invention provides a product sumcientlycoarse for handling without graining.

It is to be understood that the scope of the invention is not to belimited by the above example. The temperatures may be varied at willwithin limits of safety and practicability. Under the above conditions Iprefer to maintain the initial temperature between 85 and 90 F. and coolto between 50 and 55 F. The proportions of acetone and water and ice maybe varied between suitable limits. I prefer to dissolve 80 to 90 lbs. ofpentaerythrite tetranitrate in 300 lbs. of acetone. Any suitableequivalent solvents may be used.

The scope of my invention is also not to be limited by the illustratedapplication to the preparation of pentaerythritol tetranitrate. Asstated in the foregoing, this is merely a preferred embodiment of theinvention, chosen as a fitting illustration of the principles involvedtherein. The process may be applied in the preparation of any explosivematerial which normally exists in ,the form of a crystalline solid,provided that the stabilities and solubilities of the materials in theparticular solvents and cooling means employed do not hinder suchapplication. For example, the process of my invention may be applied tothe preparation of coarse crystals of tetranitroaniline, erythritoltetranitrate, mannitol hexanitrate, tetryl and trimethylenetrinitramine.

Acetone has been employed as the solvent in the foregoing illustration.It is to be understood however, that in a particular application of theprocess of my invention, any neutral organic solvent medium may be usedwhose properties render it suitable for the purification of theparrather than restrictive and that changes and modifications may beresorted to without departing from the spirit or the scope of the claimsappended hereto.

I claim:

1. The process for the formation of a coarse, crystallinepentaerythritol tetranitrate product containing a substantial proportionof crystals which fail to pass through a 150-mesh screen, which processcomprises forming a substantially neutral solution of pentaerythritoltetranitrate in a neutral organic solvent medium miscible with water,establishing a temperature of from 80 to 90 F. in said solution,gradually cooling said solution to between 50 and 55 F. by the gradualaddition of cold water thereto.

2. The process for the formation of a coarse, crystallinepentaerythritol tetranitrate produce containing a. substantialproportion of crystals which fail to pass through a 150-mesh screen,which process comprises forming a substantially neutral solution ofpentaerythritol tetranitrate in a neutral organic solvent mediummiscible with water, establishing a temperature of from 80 to 90 F. insaid solution, gradually cooling said solution to between 50 and 55 F.by the gradual addition of ice thereto.

3. The process for the formation of a coarse, crystallinepentaerythritol tetranitrate product containing a substantial proportionof crystals which fail to pass through a 150-mesh screen, which processcomprises forming a substantially neutral solution of pentaerythritoltetranitrate in acetone, establishing a temperature of from 80 to 90 F.in said solution, gradually cooling said solution to between 50 and. 55F. by the gradual addition of cold water thereto.

4. The process for the formation of a coarse. crystallinepentaerythritol tetranitrate product containing a substantial proportionof crystals which fail to pass through a 150-mesh screen, which processcomprises forming a substantially neutral solution of pentaerythritoltetranitrate in acetone, establishing a temperature of from 80 to 90 F.in said solution, gradually cooling said solution to between 50 and 55F. by the gradual addition of ice thereto.

5. The process for the formation of a coarse, crystallinepentaerythritol tetranitrate product containing a substantial proportionof crystals which fail to pass through a 150-mesh screen, which processcomprises dissolving pentaerythritol tetranitrate in acetone to formapproximately a 26 to 30% solution therein, establishing an initialtemperature of to F. in said solution, gradually cooling said solutionto between 50 and 55 F. by the gradual addition of cold water thereto.

6. The process for the formation of a coarse, crystallinepentaerythritol tetranitrate product containing a substantial proportionof crystals which fail to pass through a -mesh screen, which processcomprises dissolving pentaerythritol tetranitrate in acetone to formapproximately a 26 to 30% solution therein, establishing an initialtemperature of 85 to 90 F. in said solution, gradually cooling saidsolution to between 50 and 55 F. by the gradual addition of ice thereto.

7. The process for the formation of a coarse, crystallinepentaerythritol tetranitrate product containing a substantial proportionof crystals which fail to pass through a 150-mesh screen, which processcomprises dissolving approximately 90 pounds of pentaerythritoltetranitrate in 300 pounds of acetone, establishing an initialtemperature of approximately 90 F. in said solution, adding 35 pounds ofcracked ice thereto, stirring the mixture until the ice is melted,adding more ice repeatedly in approximately the same amount until thetemperature has fallen to approximately 50 F.

8. The process for the formation of a coarse crystalline pentaerythritoltetranitrate product containing a substantial proportion of crystalswhich fail to pass through a 150-mesh screen,

which process comprises forming a substantially neutral solution ofpentaerythritol tetranitrate in a neutral organic solvent miscible withwater, establishing an elevated temperature in said solution, andgradually cooling and diluting said solution by the gradual addition ofcold water thereto.

9. The process of claim 8 wherein the gradual cooling is effected by thegradual addition of 10 ice.

10. The process or the formation of a coarse crystalline pentaerythritoltetranitrate product containing a substantial proportion of crystalswhich fail to pass through a 150-mesh screen, which process comprisesforming a substantially neutral solution of pentaerythritol tetranitratein acetone, establishing an elevated temperature in said acetonesolution, and gradually cooling and diluting said solution by thegradual addition of cold water thereto.

MARSHAIL F. ACKEN.

